Device for establishing non-permanent electrical connection between an integrated circuit device lead element and a substrate

ABSTRACT

A spring contact for establishing electrical contact between a lead element of an IC device and a substrate. The spring contact generally comprises a contact portion and a base portion. The contact portion, which generally comprises a coil-type compression spring, is configured to engage and resiliently bias against a lead element of the IC device. The spring contact is disposed in a mating aperture formed in the substrate. The base portion of the spring contact is configured to secure the spring contact within the mating aperture and to establish electrical contact with the substrate. A plurality of such spring contacts and mating apertures may be arranged on the substrate in an array corresponding to the pin-out of the IC device. A clamping element secures the IC device to the substrate and biases the IC device against the spring contacts.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/934,175,filed Aug. 21, 2001, pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the assembly and testing ofintegrated circuit device components, such as multichip modules.Specifically, the present invention relates to a device and method forremovably securing an integrated circuit device to a substrate and, inparticular, to a spring contact for establishing a non-permanentelectrical connection between a lead element of an integrated circuitdevice and a substrate.

2. State of the Art

Integrated circuit (IC) devices, such as Ball Grid Array (BGA) packagesand Small Outline J-Lead (SOJ) packages, are commonly assembled intomultichip modules for connection to higher-level packaging, such as amotherboard or a personal computer chassis. Generally, a multichipmodule (MCM) includes a carrier substrate, such as a printed circuitboard, having a plurality of IC devices mounted thereto. Otherelectrical components, such as resistors, capacitors, inductors, orother suitable devices, may also be mounted on the carrier substrate ofthe MCM, or even on the IC devices. Electrical communication among theIC devices, between the IC devices and other electrical components onthe multichip module, and between the devices and external components isestablished by conductors on the MCM carrier substrate. The conductorsmay be conductive traces fabricated on the surface of, or internal to, aprinted circuit board. Methods for fabricating printed circuit boardshaving conductive traces, as well as other types of substrates havingconductors thereon, are well known in the art.

Conventional IC devices, such as BGA, TSOP, SOP, SOJ, etc. packages,generally comprise a semiconductor die electrically connected to aplurality of electrical leads that is encased within an encapsulantmaterial, a portion of each of the electrical leads extending from theencapsulant material and configured for establishing electricalconnections between the semiconductor die and external components orhigher-level packaging. An exemplary embodiment of a conventional BGApackage is shown in FIGS. 1 and 2. The conventional BGA package 10includes a semiconductor die 20 secured to a die-attach pad 35 formed onan upper surface 31 of a substrate 30, which may also be termed an“interposer.” The BGA package 10 also includes a plurality of electricalleads 40 adapted to provide electrical communication between thesemiconductor die 20 and one or more external components (not shown).The semiconductor die 20 and at least a portion of each electrical lead40 may be encased by an encapsulant material 50. The conventional BGApackage 10 may be a memory device, such as a DRAM chip, a processor, orany other integrated circuit device known in the art.

Each of the electrical leads 40 includes an external conductive ball (orbump, pillar, or other lead element) 41 configured for electricalconnection to an external component. The conductive ball 41 may besecured to a conductive pad 42 formed on a lower surface 32 of thesubstrate 30. Each electrical lead 40 further comprises a conductive via43 extending from the conductive pad 42 and through the substrate 30 toa conductive trace 44. The conductive trace 44 (only a few of which areshown in FIG. 1 for clarity) is formed on the upper surface 31 of thesubstrate 30 and provides an electrical path from the conductive via 43to a bond end 45 located proximate the semiconductor die 20. A bond wire46 attached to the bond end 45 of the conductive trace 44 and extendingto the semiconductor die 20, where the bond wire 46 is attached to abond pad thereon, electrically connects the electrical lead 40 to thesemiconductor die 20. At least the bond wire 46 and conductive trace 44of each electrical lead 40 may be encased by the encapsulant material50.

The conventional BGA package 10 may include a plurality of theconductive halls 41 arranged, for example, in an array or arrays ofmutually adjacent rows and columns. Referring to FIG. 1, the conductiveballs 41 may be arranged in two arrays 60, 70, each array 60, 70disposed between an edge of the semiconductor die 20 and a peripheraledge of the substrate 30. Each array 60, 70 comprises three columns 61,62, 63, 71, 72, 73, respectively, of conductive balls 41. Thearrangement of conductive balls 41 is typically referred to as the“pin-out” or the “footprint” of the BGA package 10. Those of ordinaryskill in the art will understand that the particular pin-out of the BGApackage 10 may vary depending upon the application and that the pin-outmay be of any suitable configuration.

To attach and electrically connect the conductive balls 41 of the BGApackage 10 to a substrate, such as, for example, an MCM carriersubstrate or a burn-in board, the substrate is configured with aplurality of contact pads arranged in a number of contact pad arrays.Each contact pad array includes a number of contact pads arranged in apattern corresponding to the pin-out of the BGA package 10. Theconductive balls 41 of the BGA package 10 may be formed of solder or aconductive or conductor-filled epoxy. If solder, the conductive balls 41are reflowed to connect to the contact pads of the contact pad array onthe substrate. If epoxy, the conductive balls 41 may be first heated toa tacky “B” stage to adhere to the contact pads, and then further heatedto completely cure the epoxy to a “C” stage. A substrate may include aplurality of IC devices mounted thereto, wherein each of the IC devicesis permanently attached to a corresponding contact pad array on asurface of the substrate. By way of example, an MCM may be a memorymodule comprised of a one-piece carrier substrate having opposingsurfaces, with one or both of the opposing surfaces of the carriersubstrates including multiple contact pad arrays and a plurality of ICdevices, such as BGA and SOJ packages, mounted thereto.

During the fabrication of an IC device, the IC device may be subjectedto individual component-level testing, such as burn-in and electricaltesting. An IC device that exhibits a desired level of performanceduring component-level testing is generally referred to as a “known gooddevice” or “known good die” while an IC device failing to meet minimumperformance characteristics may be referred to as a “known bad device.”After component-level testing, the IC device may be assembled intohigher-level packaging, such as an MCM, and again subjected to testing.Testing of higher-level packaging such as an MCM, referred to herein asmodule-level testing, may include burn-in, electrical characterizationand performance evaluation, as well as other desired electrical testing.

If an MCM fails to exhibit minimum operating characteristics duringmodule-level testing, an IC device causing the failure, which may havepreviously been identified as a “known good device” duringcomponent-level testing, must be removed from the MCM and replaced.Also, it may be desirable to introduce a “known bad” IC device into anMCM for module-level testing in order to observe the electricalcharacteristics of the MCM with the “known bad” IC device, or to observethe electrical characteristics of the “known bad” IC device at themodule level. After module-level testing is complete, the “known bad” ICdevice must be removed from the MCM and replaced. Thus, althoughindividual IC devices are typically tested at the component level, it isdesirable to subject IC devices to further testing at the module level,as a “known good device” may fail at the module level and, further,because incorporation of a “known bad device” into an MCM may be usefulin module-level testing.

To test IC devices in a higher-level environment, module-level testingis generally performed after the IC devices are assembled into andpermanently attached to, for example, an MCM carrier substrate. Thus, ifan IC device must be removed from an MCM after module-level testing, thepermanent electrical bonds between the electrical leads of the ICdevice, for example, the conductive balls 41 of the conventional BGApackage 10, and the contact pads on the MCM carrier substrate must besevered. Severing these permanent electrical bonds, which, as notedpreviously, typically comprise solder or conductive expoxy, may causeboth heat-induced and mechanical damage to the MCM carrier substrate andconductors, to the electrical leads and electrical bonds of the ICdevices remaining on the MCM, and to other electrical components mountedon the MCM.

Also, it may be necessary to remove an IC device from a substrate toachieve an upgrade. For example, as technological advances are made byIC device manufacturers, it is often desirable to replace an IC devicemounted to a substrate with a next-generation IC device exhibitingimproved performance characteristics. To replace an obsolete IC devicemounted to a substrate (such as the carrier substrate of an MCMcomprising part of, for example, a personal computer), the permanentelectrical bonds between the electrical leads of the obsolete IC deviceand a plurality of contact pads on the substrate must be severed, whichmay cause both heat-induced and mechanical damage to the substrate andto other IC devices remaining on the substrate.

To prevent heat-induced and mechanical damage resulting from severing ofthe permanent electrical bonds between the electrical leads of an ICdevice and a plurality of contact pads on a substrate, the IC device maybe non-permanently attached to the substrate for module-level testing,as well as for final assembly. Use of non-permanent connections betweenthe electrical leads of an IC device and a contact pad array of asubstrate allows for easy removal of the IC device after module-leveltesting or after final assembly without any resulting damage from thesevering of permanent electrical bonds. Sockets and fixtures fornon-permanently attaching an IC device to a substrate are well known inthe art; however, such sockets can be relatively expensive and theircost often does not justify their use. Although the cost of conventionalsockets and fixtures may, in some instances, be acceptable for limiteduse applications, such as testing and small production runs, their costis generally not acceptable for full-scale production.

Use of non-permanent electrical connections between the electrical leadsof an IC device and a contact pad array of a substrate can, however,itself cause problems during module-level testing and/or at finalassembly. Non-planarities in the substrate, in the conductors forming acontact pad array, or in the IC device itself, may, in the absence of apermanent bonding agent, result in poor electrical contact between anelectrical lead of the IC device and a corresponding contact pad on thesubstrate. For example, non-planarities in the substrate 30 of the BGApackage 10, as well as inconsistency in size of the conductive balls 41,may result in unreliable electrical contact between the conductive balls41 and the contact pads of a substrate in the absence of a permanentbonding agent. Similarly, for other types of IC devices, such as the SOJpackage, deflection of their electrical leads as they come into contactwith the contact pads on the substrate may, again, in the absence of apermanent bonding agent such as solder or conductive epoxy, result inpoor electrical contact. Poor electrical contact resulting fromnon-planarities and/or lead deflections may produce unreliable test dataduring module-level testing or prohibit the acquisition of anymeaningful test data, and such poor electrical contact may result innon-functional assembled IC device components or assembled IC devicecomponents which do not comply with customer or industry specifications.In addition, the use of non-permanent electrical connections between theelectrical leads of an IC device and a contact pad array may result inan overly long electrical path with increased inductance, acharacteristic which degrades signal integrity at high deviceoperational speeds.

Therefore, a need exists in the art for a low-cost device and method offorming non-permanent electrical connections between the electricalleads of an IC device and a contact pad array of a substrate. Such anapparatus and method must also provide for robust and reliableelectrical connections between the electrical leads of an IC device andthe contact pads on a substrate.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises embodiments of a spring contact forestablishing electrical contact between an electrical lead or leads ofan IC device and a substrate. The spring contacts may be used with anysuitable IC device, including BGA packages, SOJ packages, as well asother types of IC devices. Further, the spring contacts of the presentinvention provide a low-cost method of establishing non-permanent andreliable electrical connections between a plurality of lead elementsextending between an IC device and a substrate, such as an MCM carriersubstrate or a burn-in board.

A spring contact according to the invention generally comprises acontact portion and a base portion. The spring contact is disposed in anaperture formed in a substrate. The aperture may include both a seatportion and a base portion. A plurality of such spring contacts andmating apertures may be arranged on the substrate in an arraycorresponding to the pin-out of an IC device to be mounted on thesubstrate. The contact portion, which generally comprises a coil-typecompression spring, of the spring contact is configured to engage andresiliently bias against a lead element of an IC device. The contactportion may also be configured to align, or assist in aligning, the ICdevice lead element relative to the spring contact and substrate. Thebase portion of the spring contact is configured to secure the springcontact within the base portion of its mating aperture and to establishelectrical contact with the substrate. The seat portion of the matingaperture may also be configured to align, or assist in aligning, the ICdevice lead element relative to the spring contact and substrate. Aclamping element, such as a stab-in-place clip, is used to secure the ICdevice to the substrate and to bias the IC device against the springcontacts.

Electrical contact between the spring contact and the substrate may beestablished by disposing a layer of conductive material on at least aportion of an interior wall of the mating aperture, which may or may notextend through the substrate. A conductive trace formed on a surface ofthe substrate may be electrically connected to the layer of conductivematerial. Alternatively, a conductive filler material may be disposed inthe mating aperture, wherein the spring contact extends to, or extendsinto, the conductive filler material. A conductive trace formed on asurface of the substrate may be electrically connected to the conductivefiller material. In a further embodiment, a layer of conductive materialis disposed on at least a portion of an interior wall of the matingaperture and is electrically connected to an intermediate conductiveplane of the substrate. Electrical contact between the spring contactand the lead element of an IC device may be facilitated by providing oneor more contact elements on the spring contact, including square edges,blades, barbs, and/or roughened surfaces.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the features and advantages of this invention can be more readilyascertained from the following detailed description of the inventionwhen read in conjunction with the accompanying drawings, in which:

FIG. 1 shows a plan view of an exemplary embodiment of a conventionalBGA package;

FIG. 2 shows a cross-sectional view of the conventional BGA package astaken along line II—II of FIG. 1;

FIG. 3 shows a plan view of a substrate including a plurality of springcontacts according to an embodiment of the invention;

FIG. 4 shows a cross-sectional view of the substrate including aplurality of spring contacts according to the invention as taken alongline IV—IV of FIG. 3;

FIG. 5 shows a cross-sectional view of the substrate including aplurality of spring contacts according to the invention as taken alongline IV—IV of FIG. 3, and further including a conventional BGA packageas shown in FIGS. 1 and 2;

FIG. 6 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 7 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 8 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 9 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 10 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 11 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 12 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 12A shows a cross-sectional view of a spring contact according toan embodiment of the invention having the spring coils in contact;

FIG. 13 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 13A shows a cross-sectional view of a spring contact according toan embodiment of the invention having the spring coils in contact;

FIG. 14 shows a cross-sectional view of a spring contact according to anembodiment of the invention;

FIG. 14A shows a cross-sectional view of a spring contact according toan embodiment of the invention having the spring coils in contact;

FIG. 15 shows a cross-sectional view of a multichip module incorporatinga plurality of spring contacts according to the invention; and

FIG. 16 shows a partial cross-sectional view of a spring contactaccording to the present invention in conjunction with a conventionalSOJ package.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIGS. 3 through 6 is an embodiment of a spring contactaccording to the present invention for establishing electrical contactbetween a lead element of an IC device, such as the conventional BGApackage 10 shown in FIGS. 1 and 2, and a substrate. Although theembodiments of a spring contact of the present invention are describedherein in the context of mounting and electrically connecting a BGApackage to a substrate, those of ordinary skill in the art willunderstand that the spring contacts of the instant invention may be usedwith other types of IC devices, such as, for example, an SOJ package. Asused herein, the term “lead element” refers to and encompasses any typeof conductive ball, pillar, or bump extending from an IC device, as wellas a lead finger extending from an IC device having leadframeconstruction, such as, for example, an SOJ package.

Referring to FIGS. 3 and 4, a one-piece substrate 160 includes aplurality of spring contacts 120 disposed thereon and arranged in rowsand columns to form a two-dimensional array 121 of spring contacts 120corresponding to the footprint of a BGA package, such as theconventional BGA package 10 (shown in FIGS. 3 and 4 in dashed line).Each spring contact 120 is disposed in a mating aperture 170 formed inthe substrate 160, and the substrate 160 includes a plurality of suchapertures 170 arranged in an array 171 corresponding to thetwo-dimensional array 121 of spring contacts 120 to be disposed therein,respectively.

The substrate 160 may comprise an MCM carrier substrate and, further,may be constructed of a printed circuit board (PCB) material accordingto conventional, well-known PCB fabrication techniques. However, it willbe appreciated by those of ordinary skill in the art that the substrate160 may be adapted to applications other than an MCM. For example, thesubstrate 160 may comprise a test board, such as a burn-in board, or aportion thereof. Also, the substrate 160 may be constructed of any othersuitable dielectric or non-conducting materials, including plastics,resins, composites, glasses, ceramics, silicon, other oxide materials,etc.

Each spring contact 120 is configured to engage and resiliently biasagainst an individual conductive ball 41 of the BGA package 10 in orderto establish physical and electrical contact between the conductive ball41 and the spring contact 120. Referring to FIG. 5, the conventional BGApackage 10 is shown mounted to the substrate 160. Each conductive ball41 of the BGA package 10 is engaged with and specifically, asillustrated, at least partially received within a contact portion 122 ofa corresponding spring contact 120 disposed on the substrate 160, thearray 121 of spring contacts 120, as well as the array 171 of apertures170, being arranged in a pattern matching the pin-out of the conductiveballs 41 extending from the BGA package 10. Thus, an electricalconnection is formed between each conductive ball 41 of the BGA package10 and one of the spring contacts 120 disposed on the substrate 160.Additionally, compression of the spring contacts 120 as BGA package 10is disposed against substrate 160 will help to reduce inductiveelectrical effects as the spring contacts 120 are compressed andlaterally adjacent coils or segments thereof are placed in mutualcontact to effectively shorten the electrical path and reduceinductance.

To secure the BGA package 10 to the substrate 160 and to create bothphysical and electrical contact between each conductive ball 41 and amating spring contact 120, the BGA package 10 is held against thesubstrate 160, and biased against the spring contacts 120, by a clampingelement 90. The clamping element 90 illustrated in FIG. 5 may be anysuitable clip or clamp known in the art adapted to secure the BGApackage 10 to the substrate 160. For example, the clamping element 90may comprise a stab-in-place clip 95 having one or more resilient tabsor prongs 96 configured for insertion into corresponding holes 164 inthe substrate 160. The resilient tab or tabs 96 are retained by thecorresponding hole or holes 164 to secure the BGA package 10 to thesubstrate 160 and to bias the conductive balls 41 thereof against thespring contacts 120. Typically, such stab-in-place type clips 95 areinjection molded from plastic materials and are relatively inexpensive.In addition to the foregoing, it is also contemplated that variousapparatus disclosed and claimed in copending U.S. patent applicationSer. No. 09/478,619, filed Jan. 5, 2000 and assigned to the assignee ofthe present invention, may be employed to secure BGA package 10 to thesubstrate 160. The disclosure of U.S. patent application Ser. No.09/478,619 is hereby incorporated herein by reference.

Referring to FIG. 6, each spring contact 120 includes a contact portion122 and a base portion 124. The contact portion 122 is configured toengage and resiliently bias against a conductive ball 41 of the BGApackage 10 and to thereby establish physical and electrical contact withthe conductive ball 41. The contact portion 122 generally comprises acoil-type compression spring, as is shown in FIGS. 4 through 6. The baseportion 124 is configured to secure the spring contact 120 within itsmating aperture 170 and to establish electrical contact between thespring contact 120 and the substrate 160. The base portion 124 maycomprise an S-shaped cantilever-type spring, as is shown in FIGS. 4through 6; however, the base portion 124 may comprise any other suitableshape and configuration, so long as the base portion 124 can be securedin the aperture 170 and form electrical contact therewith.

The contact portion 122 may be further configured to align, or to assistin aligning, the conductive ball 41 relative to the spring contact 120.For example, as shown in FIG. 6, the contact portion 122 may comprise agenerally hemispherically or conically shaped coil spring providing acup or recess 123 for receiving at least a portion of the conductiveball 41. The cup or recess 123 provided by the contact portion 122functions to guide or align the conductive ball 41 relative to thespring contact 120, and relative to the substrate 160, as the conductiveball 41 engages the contact portion 122 of the spring contact 120. Thecontact portion 122 may be of any other suitable shape adapted to alignthe conductive ball 41 relative to the spring contact 120.

Each aperture 170 in substrate 160 may include a seat portion 172 and aretaining portion 174. The seat portion 172 is configured to receive thecontact portion 122 of a spring contact 120. The seat portion 172generally comprises a recess formed in one surface 167 of the substrate160. The retaining portion 174 is configured to receive and retain thebase portion 124 of the spring contact 120 and to establish electricalcontact with the spring contact 120. The retaining portion 174 generallycomprises a via extending from the seat portion 172 through thesubstrate 160 and opening to a second opposing surface 168 of thesubstrate 160.

To secure a spring contact 120 within its mating aperture 170 of thesubstrate 160, the base portion 124 of the spring contact 120 isinserted into the retaining portion 174 of the aperture 170. The baseportion 124 of spring contact 120 makes contact with the retainingportion 174 of aperture 170 and mutual contact forces therebetween, suchmutual contact forces resulting from deflection of the base portion 124upon insertion into the retaining portion 174, create frictional forcesthat retain the spring contact 120 within the aperture 170.Alternatively, the base portion 124 of a spring contact 120 may besecured within the retaining portion 174 of a mating aperture 170 usinga permanent bonding agent, such as solder or a conductive epoxy.

To establish electrical contact between the retaining portion 174 of anaperture 170 and the base portion 124 of a spring contact 120, theretaining portion 174 may, for example, include a layer of conductivematerial 176 disposed on at least a portion of an interior wall of theretaining portion 174. The layer of conductive material 176 may compriseany suitable conductive material and may be formed or deposited usingany suitable process known in the art. A conductive trace 166 disposedor formed on the second opposing surface 168 of the substrate 160 may beelectrically connected to the layer of conductive material 176.

The seat portion 172 may be further configured to align, or assist inaligning, the conductive ball 41 relative to the spring contact 120. Forexample, as shown in FIG. 6, the seat portion 172 may comprise agenerally hemispherical recess. As the conductive ball 41 engages thespring contact 120, the hemispherical recess guides the conductive ball41 (shown in dashed line in FIG. 6) into contact with the contactportion 122 of the spring contact 120. Therefore, such a hemisphericalrecess functions to align, or assist in aligning, the conductive ball 41relative to the spring contact 120, as well as relative to the substrate160. The seat portion 172 may be any other suitable shape adapted toguide the conductive ball 41 into contact with the contact portion 122of a spring contact 120.

Referring to FIG. 7, a spring contact 220 according to anotherembodiment of the invention is shown. The spring contact 220 comprises acontact portion 222 and a base portion 224. The base portion 224 issecured within a retaining portion 274 of an aperture 270 formed in asubstrate 260. The aperture 270 also includes a seat portion 272generally comprising a recess formed in one surface 267 of the substrate260. The spring contact 220 and mating aperture 270 shown in FIG. 7 aresimilar to the spring contact 120 and aperture 170 shown in FIGS. 3through 6; however, the contact portion 222 of spring contact 220comprises a generally cylindrically shaped coil spring providing a cupor recess 223 for receiving at least a portion of a conductive ball 41.The cup or recess 223 provided by the contact portion 222 functions toguide or align the conductive ball 41 relative to the spring contact 220and substrate 260 as the conductive ball 41 engages the contact portion222 of the spring contact 220. Also, the seat portion 272 of aperture270 comprises a generally conical shape for aligning, or assisting inalignment of, the conductive ball 41 (shown in dashed line in FIG. 7)relative to the spring contact 220.

In another alternative embodiment of the invention, as shown in FIG. 7,the aperture 270 is at least partially filled with a conductive fillermaterial 280. The base portion 224 of the spring contact 220 extends to,or extends into, the conductive filler material 280 to establishelectrical connection therebetween. A conductive trace 266 formed on asurface 268 of the substrate 260 may be electrically connected to theconductive filler material 280 disposed within the aperture 270. Itshould be noted that the conductive filler material 280 may itselffunction to secure the spring contact 220 within the aperture 270. Theconductive filler material 280 may be any suitable conductive materialknown in the art, including solder materials and conductive orconductor-filled epoxies.

Referring to FIG. 8, a spring contact 320 according to anotherembodiment of the invention is shown. The spring contact 320 comprises acontact portion 322 and a base portion 324. The base portion 324 issecured within a retaining portion 374 of an aperture 370 formed in asubstrate 360. The aperture 370 also includes a seat portion 372generally comprising a recess formed in one surface 367 of substrate360. A layer of conductive material 376 is formed on at least a portionof an interior wall of the retaining portion 374 for establishingelectrical contact with the spring contact 320. A conductive trace 366may be formed on a surface 368 of the substrate 360 and electricallyconnected to the layer of conductive material 376.

The spring contact 320 and mating aperture 370 shown in FIG. 8 are,therefore, similar to the spring contact 120 and aperture 170 shown inFIGS. 3 through 6; however, the contact portion 322 of spring contact320 comprises a generally cone-shaped coil spring having an apex orpoint 323 for contacting and/or penetrating the outer surface of aconductive ball 41 (shown in dashed line in FIG. 8). The apex or point323 can penetrate or puncture any layer of oxide or other contaminantsformed on the exterior surface of conductive ball 41, such that reliableelectrical contact can be established between the spring contact 320 andthe conductive ball 41. It should be understood that any suitable typeof apex or point 323 capable of penetrating or puncturing a layer orlayers of oxide or contaminates on the conductive ball 41 may be used.Also, the seat portion 372 of aperture 370 comprises a generallycylindrical shape for aligning the conductive ball 41 relative to thespring contact 320. It should be noted that, for the embodiment shown inFIG. 8, alignment of the conductive ball 41 relative to the springcontact 320 and substrate 360 is performed primarily by the seat portion372 of the aperture 370.

Referring to FIG. 9, a spring contact 420 according to anotherembodiment of the invention is shown. The spring contact 420 comprises acontact portion 422 and a base portion 424. The base portion 424 issecured within an aperture 470 formed in a substrate 460. The springcontact 420 shown in FIG. 9 is similar to the spring contact 120 shownin FIGS. 3 through 6; however, the aperture 470 receiving the springcontact 420 does not include a seat portion. Rather, the contact portion422 of the spring contact 420 extends substantially entirely above asurface 467 of the substrate 460. A layer of conductive material 476 isformed on at least a portion of an interior wall of the aperture 470 forestablishing electrical contact with the spring contact 420. Aconductive trace 466 may be formed on an opposing surface 468 of thesubstrate 460 and electrically connected to the layer of conductivematerial 476. For the embodiment shown in FIG. 9, alignment of theconductive ball 41 (shown in dashed line in FIG. 9) relative to thespring contact 420 and substrate 460 is performed primarily by thecontact portion 422 of the spring contact 420, which may include a cupor recess 423 for aligning the conductive ball 41 relative thereto.

Referring to FIG. 10, a spring contact 520 according to anotherembodiment of the invention is shown. The spring contact 520 comprises acontact portion 522 and a base portion 524. The spring contact 520 shownin FIG. 10 is similar to the spring contact 120 shown in FIGS. 3 through6; however, the base portion 524 of the spring contact 520 is securedwithin a hole 570 formed in a substrate 560, wherein the hole 570 doesnot extend through the substrate 560. The hole 570, which includes aseat portion 572 and a retaining portion 574, opens only to a surface567 of the substrate 560 and does not extend to an opposing surface 568thereof. A layer of conductive material 576 is formed on at least aportion of an interior wall of the seat portion 572 and at least aportion of an interior wall of the retaining portion 574 forestablishing electrical contact with the spring contact 520. Aconductive trace 566 may be formed on the surface 567 of the substrate560 and electrically connected to the layer of conductive material 576.For the embodiment shown in FIG. 10, alignment of the conductive ball 41(shown in dashed line in FIG. 10) relative to the spring contact 520 andsubstrate 560 is performed primarily by the contact portion 522 of thespring contact 520, which may include a cup or recess 523 for aligningthe conductive ball 41 relative thereto.

Referring to FIG. 11, a spring contact 620 according to anotherembodiment of the invention is shown. The spring contact 620 comprises acontact portion 622 and a base portion 624. The spring contact 620 shownin FIG. 11 is similar to the spring contact 120 shown in FIGS. 3 through6; however, the base portion 624 of the spring contact 620 is securedwithin a hole 670 formed in a substrate 660, wherein the hole 670 doesnot extend through the substrate 660. The hole 670, which includes aseat portion 672 and a retaining portion 674, opens only to a surface667 of the substrate 660 and does not extend to an opposing surface 668thereof. A layer of conductive material 676 is formed on at least aportion of an interior wall of the retaining portion 674 forestablishing electrical contact with the spring contact 620. Anintermediate conductive plane or traces 669 may be formed within thethickness of the substrate 660, and the intermediate conductive plane ortraces 669, or portions thereof, are electrically connected to the layerof conductive material 676. For the embodiment shown in FIG. 11,alignment of the conductive ball 41 (shown in dashed line in FIG. 11)relative to the spring contact 620 and substrate 660 is performedprimarily by the contact portion 622 of the spring contact 620, whichmay include a cup or recess 623 for aligning the conductive ball 41relative thereto.

The spring contacts 120, 220, 320, 420, 520, 620 may be constructed ofany suitable material exhibiting sufficient resiliency and conductivity.For example, the spring contacts 120, 220, 320, 420, 520, 620 maycomprise a beryllium copper material, as well as other copper alloymaterials. Generally, the contact portion 122, 222, 322, 422, 522, 622and base portion 124, 224, 324, 424, 524, 624 will be constructed from asingle piece of material, such as beryllium copper wire. However, it iswithin the scope of the present invention that the contact portion 122,222, 322, 422, 522, 622 and base portion 124, 224, 324, 424, 524, 624may be constructed as separate parts that are subsequently joinedtogether.

Also, in a further embodiment of the invention, the spring contacts 120,220, 320, 420, 520, 620 may include, or be constructed from aresiliently conductive wire that includes, one or more contact elementsconfigured to wipe away and/or puncture a layer of oxide and/or othercontaminants formed on an exterior surface of a conductive ball 41. Forexample, as shown in FIG. 12, a spring contact 720 may be constructedfrom a wire material exhibiting a rectangular cross-section and having aplurality of sharp edges 728 that may function as contact elements. Thesharp edges 728 can impinge against and move over the exterior surfaceof a conductive ball 41, effecting a scraping or penetrating action toremove oxides and other contaminants therefrom or to reach interiorportions of conductive ball 41. Alternatively shaped wire, such as onehaving a triangular cross-section, is also believed suitable for thispurpose.

As illustrated in FIG. 12A, the coils 720′ of the spring contact 720 areshown in contact with each other when the spring contact 720 is in acollapsed state.

Referring to FIG. 13, a spring contact 820 is constructed from a wirematerial having a plurality of longitudinally extending blades 828 thatmay function as contact elements. The longitudinally extending blades828 can impinge against and move over the exterior surface of aconductive ball 41 to remove oxides and other contaminants therefrom.Blades extending circumferentially or helically about the wire materialare also believed suitable for this purpose.

As illustrated in FIG. 13A, the coils 820′ of the spring contact 820 areshown in contact with each other when the spring contact 820 is in acollapsed state.

As shown on the right-hand side of FIG. 14, a spring contact 920 a maybe constructed from a wire material having a plurality of barbs orprotrusions 928 a extending from an outer cylindrical surface thereof.The barbs or protrusions 928 a can impinge against and puncture throughlayers of oxide and other contaminants on the exterior surface of aconductive ball 41 to form electrical contact therewith. Similarly, asshown on the left-hand side of FIG. 14, a spring contact 920 b may beconstructed from a wire material simply having a roughened outer surface928 b. The roughened outer surface 928 b can impinge against and moveover the exterior surface of a conductive ball 41 to remove oxides andother contaminants therefrom.

As illustrated in FIG. 14A, the coils 920′ of the spring contact 920 aare shown in contact with each other when the spring contact 920 a is ina collapsed state.

It should be noted that the contact elements 728, 828, 928 a, 928 b maybe used in combination with one another. For example, a spring contactmay be constructed from a wire material including one or morelongitudinally extending blades and also including a plurality of barbsor protrusions. Also, the contact elements 728, 828, 928 a, 928 b may beused in conjunction with IC devices having electrical lead elementsother than conductive balls, such as, for example, an SOJ package.

Those of ordinary skill in the art will appreciate that the variousfeatures of the spring contacts 120, 220, 320, 420, 520, 620, 720, 820,920 a, 920 b shown and described with respect to FIGS. 3 through 14 maybe used in any suitable combination. A spring contact having any type ofcontact portion, i.e., a generally hemispherical or conical shape, agenerally cylindrical shape, or a cone-shape having an apex, may be usedin conjunction with any type of aperture, i.e., one having ahemispherically shaped seat portion, a conically shaped seat portion, acylindrically shaped seat portion, or no seat portion. For example, acone-shaped contact portion having an apex (see FIG. 8) may be used withan aperture having a hemispherical shape (see FIG. 6) or a conical shape(see FIG. 7).

Also, for any spring contact according to the present invention,electrical contact between a spring contact and mating aperture formedin a substrate may be established according to any of the embodimentsdescribed herein, i.e., a layer of conductive material on an interiorwall of the aperture in conjunction with a conductive trace on a surfaceof the substrate, a conductive filler material within the aperture inconjunction with a conductive trace on a surface of the substrate, alayer of conductive material on an interior wall of a hole partiallyextending into the substrate in conjunction with a conductive trace on asurface of the substrate, or a layer of conductive material on aninterior wall of a hole partially extending into the substrate inconjunction with an intermediate conductive plane of the substrate, orany combination thereof. For example, a conductive filler material (seeFIG. 7) may be used in conjunction with an intermediate conductive plane(see FIG. 11) or, alternatively, a spring contact may be configured toestablish direct contact with an intermediate conductive plane.

Referring to FIG. 15, an MCM 1000 incorporating a plurality of springcontacts 1020 according to the present invention is shown. The MCM 1000includes a one-piece carrier substrate 1060 having one or more BGApackages 10 a mounted to a surface 1067 thereof and having one or moreBGA packages 10 b mounted to an opposing surface 1068 thereof. AlthoughIC devices are shown mounted to both surfaces 1067, 1068 of the carriersubstrate 1060, those of ordinary skill in the art will understand thatthe MCM 1000 may have IC devices mounted to only one of its carriersubstrate surfaces 1067, 1068. The BGA packages 10 a, 10 b are securedto the carrier substrate 1060 by clamping elements 90, which are shownas stab-in-place clips in FIG. 15. In addition, U.S. patent applicationSer. No. 09/478,619, the disclosure of which has been previouslyincorporated herein by reference, discloses and claims apparatusespecially suitable for nonpermanently connecting integrated circuitdevices such as BGA packages 10 a, 10 b to MCM substrates such ascarrier substrate 1060.

To electrically connect the BGA packages 10 a, 10 b to the carriersubstrate 1060 of the MCM 1000, each of the conductive balls 41 a, 41 bon the BGA packages 10 a, 10 b, respectively, is engaged with a matingspring contact 1020 disposed on the MCM carrier substrate 1060. Thespring contacts 1020 are retained in respective apertures 1070 formed inthe carrier substrate 1060. A spring contact 1020 and mating aperture1070 may comprise any of the spring contacts 120, 220, 320, 420, 520,620, 720, 820, 920 a, 920 b and mating apertures 170, 270, 370, 470, orholes 570, 670 described herein, or include any combination of featuresdescribed herein.

Although the spring contacts 120, 220, 320, 420, 520, 620, 720, 820, 920a, 920 b according to the present invention have been described hereinin the context of establishing electrical connections with theconductive balls 41 of a conventional BGA package 10, it should beunderstood by those of ordinary skill in the art that the presentinvention is not so limited. The spring contacts 120, 220, 320, 420,520, 620, 720, 820, 920 a, 920 b may be used to electrically connect thelead elements of other types of IC packages to a substrate. For example,as shown in FIG. 16, a spring contact 1120 may be used to electricallyconnect a lead element or lead finger 82 extending from an SOJ package80 to a substrate 1160. The spring contact 1120 includes a contactportion 1122 and a base portion 1124, the base portion 1124 beingretained in a retaining portion 1174 of a corresponding aperture 1170.The aperture 1170 also includes a seat portion 1172. The spring contact1120 and mating aperture 1170 may comprise any of the spring contacts120, 220, 320, 420, 520, 620, 720, 820, 920 a, 920 b and matingapertures 170, 270, 370, 470, or holes 570, 670 described herein,respectively, or include any combination of features described herein.

A spring contact according to the present invention having been hereindescribed, those of ordinary skill in the art will appreciate the manyadvantages of the present invention. The spring contacts of the presentinvention provide robust and reliable non-permanent electricalconnections between a lead element or elements extending between an ICdevice and a substrate, such as an MCM carrier substrate. The electricalconnection provided by such a spring contact can be easily severedwithout mechanical- or heat-induced damage. Also, use of spring contactsaccording to the invention enables IC devices to be directly attached toa substrate, without the need for relatively expensive sockets. Further,any of the spring contacts described herein may be used for testingapplications, such as, for the temporary mounting of IC devices to abum-in or other test board or for final assembly of an electricalcomponent, such as an MCM.

The foregoing detailed description and accompanying drawings are onlyillustrative and are not restrictive. They have been provided primarilyfor a clear and comprehensive understanding of the present invention andno unnecessary limitations are to be understood therefrom. Numerousadditions, deletions, and modifications to the embodiments describedherein, as well as alternative arrangements, may be devised by thoseskilled in the art without departing from the spirit of the presentinvention and the scope of the appended claims.

1. An electrical component, comprising: at least one IC device having a plurality of lead elements extending therefrom; a substrate having a first surface and an opposing second surface; a plurality of apertures opening onto at least the first surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the at least one IC device, each aperture of the plurality of apertures comprising: a seat portion comprising a generally hemispherical recess having a maximum lateral dimension in the first surface; and a retaining portion comprising a via of a lateral dimension lesser than the maximum lateral dimension of the seat portion, the via extending from the seat portion toward the second surface of the substrate; a plurality of spring contacts, each spring contact of the plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a generally hemispherically shaped resiliently compressible coil spring having a maximum lateral dimension greater than the lateral dimension of the via, and the base portion extending longitudinally therefrom, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture and the base portion thereof extending into and secured entirely within the retaining portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some of the spring contacts of the plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the at least one IC device; and at least one clamping element securing the at least one IC device to the substrate and biasing each lead element of the plurality of lead elements of the at least one IC device against the contact portion of one spring contact of the plurality of spring contacts.
 2. The electrical component of claim 1, wherein the base portion of each spring contact is secured within the retaining portion of each aperture by frictional forces.
 3. The electrical component of claim 1, wherein the base portion of the spring contact is secured within the retaining portion of each aperture by an electrically conductive bonding agent.
 4. The electrical component of claim 1, wherein the at least one clamping element comprises a stab-in-place clip extending over the at least one IC device and including prongs extending transversely therefrom and received within holes in the substrate.
 5. The electrical component of claim 1, wherein each resiliently compressible coil spring includes at least two coils contacting portions of each other as biased against and electrically contacting one lead element of the plurality of lead elements of the at least one IC device.
 6. The electrical component of claim 1, further comprising: a second IC device having a plurality of lead elements extending therefrom; a second plurality of apertures opening onto at least the second surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the second IC device, each aperture of the second plurality of apertures comprising a seat portion comprising a recess in the second surface having a retaining portion comprising a via of lesser lateral dimension extending from the seat portion toward the first surface of the substrate; a second plurality of spring contacts, each spring contact of the second plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a resiliently compressible coil spring and the base portion extending longitudinally therefrom, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture of the second plurality and the base portion thereof extending into and secured within the base portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some spring contacts of the second plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the second IC device; and at least another clamping element securing the second IC device to the substrate and biasing each lead element of the plurality of lead elements of the second IC device against the contact portion of one spring contact of the second plurality of spring contacts.
 7. An electrical component, comprising: at least one IC device having a plurality of lead elements extending therefrom; a substrate having a first surface and an opposing second surface; a plurality of apertures opening onto at least the first surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the at least one IC device, each aperture of the plurality of apertures comprising: a seat portion comprising a generally conically shaped recess having a maximum lateral dimension in the first surface; and a retaining portion comprising a via of a lateral dimension lesser than the maximum lateral dimension of the seat portion, the via extending from the seat portion toward the second surface of the substrate; a plurality of spring contacts, each spring contact of the plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a generally cylindrically shaped resiliently compressible coil spring having a lateral dimension greater than the lateral dimension of the via, and the base portion extending longitudinally therefrom, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture and the base portion thereof having a lesser lateral dimension extending into and secured entirely within the retaining portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some of the spring contacts of the plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the at least one IC device; and at least one clamping element securing the at least one IC device to the substrate and biasing each lead element of the plurality of lead elements of the at least one IC device against the contact portion of one spring contact of the plurality of spring contacts.
 8. The electrical component of claim 7, wherein the base portion of each spring contact is secured within the retaining portion of each aperture by frictional forces.
 9. The electrical component of claim 7, wherein the base portion of the spring contact is secured within the retaining portion of each aperture by an electrically conductive bonding agent.
 10. The electrical component of claim 7, wherein the at least one clamping element comprises a stab-in-place clip extending over the at least one IC device and including prongs extending transversely therefrom and received within holes in the substrate.
 11. The electrical component of claim 7, wherein each resiliently compressible coil spring includes at least two coils contacting portions of each other as biased against and electrically contacting one lead element of the plurality of lead elements of the at least one IC device.
 12. The electrical component of claim 7, further comprising: a second IC device having a plurality of lead elements extending therefrom; a second plurality of apertures opening onto at least the second surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the second IC device, each aperture of the second plurality of apertures comprising a seat portion comprising a recess in the second surface having a retaining portion comprising a via of lesser lateral dimension extending from the seat portion toward the first surface of the substrate; a second plurality of spring contacts, each spring contact of the second plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a resiliently compressible coil spring and the base portion extending longitudinally therefrom, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture of the second plurality and the base portion thereof extending into and secured within the base portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some spring contacts of the second plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the second IC device; and at least another clamping element securing the second IC device to the substrate and biasing each lead element of the plurality of lead elements of the second IC device against the contact portion of one spring contact of the second plurality of spring contacts.
 13. An electrical component, comprising: at least one IC device having a plurality of lead elements extending therefrom; a substrate having a first surface and an opposing second surface; a plurality of apertures opening onto at least the first surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the at least one IC device, each aperture of the plurality of apertures comprising: a seat portion comprising a generally cylindrically shaped recess having a lateral dimension in the first surface; and a retaining portion comprising a via of a lateral dimension lesser than the seat portion lateral dimension, the via extending from the seat portion toward the second surface of the substrate; a plurality of spring contacts, each spring contact of the plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a generally cone shaped resiliently compressible coil spring having an apex configured for contacting the outer surface of a lead element of the plurality, a maximum lateral dimension of the contact portion greater than the lateral dimension of the via, the base portion extending longitudinally from the contact portion, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture and the base portion thereof extending into and secured entirely within the retaining portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some of the spring contacts of the plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the at least one IC device; and at least one clamping element securing the at least one IC device to the substrate and biasing each lead element of the plurality of lead elements of the at least one IC device against the contact portion of one spring contact of the plurality of spring contacts.
 14. The electrical component of claim 13, wherein the base portion of each spring contact is secured within the retaining portion of each aperture by frictional forces.
 15. The electrical component of claim 13, wherein the base portion of the spring contact is secured within the retaining portion of each aperture by an electrically conductive bonding agent.
 16. The electrical component of claim 13, wherein the at least one clamping element comprises a stab-in-place clip extending over the at least one IC device and including prongs extending transversely therefrom and received within holes in the substrate.
 17. The electrical component of claim 13, wherein each resiliently compressible coil spring includes at least two coils contacting portions of each other as biased against and electrically contacting one lead element of the plurality of lead elements of the at least one IC device.
 18. The electrical component of claim 13, further comprising: a second IC device having a plurality of lead elements extending therefrom; a second plurality of apertures opening onto at least the second surface of the substrate and arranged in a pattern corresponding to a footprint of the plurality of lead elements extending from the second IC device, each aperture of the second plurality of apertures comprising a seat portion comprising a recess in the second surface having a retaining portion comprising a via of lesser lateral dimension extending from the seat portion toward the first surface of the substrate; a second plurality of spring contacts, each spring contact of the second plurality of spring contacts including a base portion and a contact portion, the contact portion comprising a resiliently compressible coil spring and the base portion extending longitudinally therefrom, the contact portion of each spring contact being at least partially received within and supported by the seat portion of an aperture of the second plurality and the base portion thereof extending into and secured within the base portion of the aperture and electrically connected to the substrate; wherein the resiliently compressible coil spring of the contact portions of at least some spring contacts of the second plurality of spring contacts are biased against and electrically contacting lead elements of the plurality of lead elements of the second IC device; and at least another clamping element securing the second IC device to the substrate and biasing each lead element of the plurality of lead elements of the second IC device against the contact portion of one spring contact of the second plurality of spring contacts. 